Strength of Materials

Students begin by drawing the diagrams of axial forces, shear forces, and bending moments in beams or bars subjected to concentrated loads, distributed loads, and applied moments. They determine the geometric centroid, the moment of inertia, and the first moment of area for transverse sections. The fundamental concepts and equations of Strength of Materials are taught, enabling the calculation of stresses and strains in simple structures.

These notions are complemented by the material strength limit and the use of the safety factor in determining the allowable stress of a component made from that material. The study of structural elements subjected to axial loads, torsion, and bending is taught using analytical and graphical tools, supported by theoretical-practical exercises involving real engineering problems organized in increasing order of difficulty. This study is strongly supported by practical work carried out in laboratory classes.

The teaching methodology of the curricular unit will be predominantly student-centered, making use of structural components from everyday applications, which students, individually or in groups, must analyse and understand within the scope of mechanical concepts.

The foundations for introducing the core concepts involve the use of various types of presentation and discussion methodologies. Accordingly, the following will be implemented:

• Presentation of content using electronic slides, made available to students as complementary documentation supporting the curricular unit.

• Viewing of multimedia content.

• Observation of structural components and assemblies relevant to the curricular unit.

• Visits to metallic structures located in the surroundings of ISEC.

Students will be presented with several challenges, contextualised within the different domains of the curricular unit. These challenges involve understanding the behaviour of certain structural elements used in everyday applications, as well as the design, development and construction of structural elements for defined objectives.

Additionally, application exercises covering each concept of the curricular unit will be solved, serving as the basis for knowledge acquisition and for the development of the proposed challenges.

The course Strength of Materials aims to study, as extensively as possible, the behaviour of structural elements used in mechanical and metallic construction, taking into account their operating conditions and the types of loads to which they are subjected. Determining the most suitable material, the most appropriate shape and dimensions to withstand the various types of external loads applied to machines, components, structural parts, etc., at the lowest possible cost and with maximum safety, clearly defines what is required from the student as a future engineer.

Competencies: Understand the concepts and procedures involved in the selection and design of machine elements and structural members. Know and be able to use measurement and control instrumentation. Be able to design mechanical components and planar truss structures.

1 – Statics1.1 – Mechanical action on a mechanical structure

Mechanical actions applied to a structure: concentrated forces and distributed forces; moments (moment of a force and couple of forces). Types of structural supports.

1.2 – Static equilibrium of a mechanical structure

Degrees of freedom of a body. Types of structural supports (roller, pin, and fixed/encastre). Equilibrium of a particle. Linear elastic spring. Cables and pulleys. Determination of support reactions in an isostatic structure. Equilibrium of a rigid body. Free-body diagram. Determination of support reactions in an isostatic structure – straight-axis beam.

1.3 – Internal forces developed in a mechanical structure

Axial forces, shear forces, bending moments and torsional moments.

2 – Basic Concepts of Strength of Materials

Concept of stress: normal stress and shear stress. Concepts of displacement and strain. Electrical resistance strain gauge. Hooke’s Law. Stress-strain diagrams for ductile and brittle materials. Concepts of elasticity and plasticity. Mechanical properties of materials. Principle of superposition of force effects. Strain energy (elastic potential energy). Concepts of resilience and toughness of a material. Basic structural design. Notion of safety factor.

3 – Structural Elements Subjected to Axial Loads

Stresses in axially loaded bars. Saint-Venant’s principle. Bar elongation. Influence of temperature on bar elongation. Simple planar truss.

4 – Structural Elements Subjected to Torsion

Pure shear. Torsion in circular and non-circular cross-sections. Thin-walled closed sections. Power transmitted from a motor to a shaft.

5 – Structural Elements Subjected to Bending

Relationships between distributed load, shear force and bending moment. Shear force and bending moment diagrams for straight-axis structures. Bending of straight beams/bars: pure bending, simple bending. Normal stresses in compression and tension. Neutral axis equation. Shear stresses in bending. Static moment for circular, rectangular, T-shaped and I-shaped cross-sections. Calculation of beam deflections using practical tables.

Assessment Methods

The curricular unit operates under two possible assessment regimes: a) Continuous Assessment; b) Final Examination Assessment.

Until the second week of the semester, students must choose the assessment regime they intend to follow.

a) Continuous Assessment

Under the continuous assessment regime, the curricular unit includes:

The completion of a set of Case Studies, which may involve experimentation, oral presentation and discussion, carried out individually or in groups during class time. The case studies must be presented in the form of a written report (handwritten or produced using a word processor) or through other communication and presentation formats, such as Poster format.

These activities are carried out during laboratory classes and account for 25% of the final grade of the curricular unit, meaning the set of case studies is worth 5 points. Attendance in classes is not mandatory, nor is a minimum grade required in the case studies. The use of Artificial Intelligence (AI) is not permitted. In the exam, a minimum grade of 7 points (on a scale of 0 to 15) is required.

Final Classification: Exam * 75% + Case Studies

b) Final Examination Assessment

Exam: 100%, with a mandatory minimum grade of 9.5 points on a scale of 0 to 20. The use of Artificial Intelligence (AI) is not permitted.

Final Classification: Exam * 100%

NAO